1. Field of the Invention
Embodiments of the invention relate to a display device, and more particularly, to a display device including a line on glass (LOG) for transmitting a power and a signal between printed circuit boards.
2. Discussion of the Related Art
Among various display devices, flat panel displays (FPDs) such as a liquid crystal display (LCD) device, a plasma display panel (PDP) and an organic light emitting diode (OLED) display device have been widely used. In general, a display device includes a display panel displaying an image, a driving circuit unit supplying a power and a signal to the display panel and a frame surrounding and integrating the display panel and the driving circuit unit. The driving circuit unit is connected to the display panel and supplies a plurality of powers and a plurality of signals to the display panel.
The driving circuit unit may include a printed circuit board (PCB) where a timing controlling part and a power part are mounted and a flexible film where a data driving part is mounted. The driving circuit unit will be illustrated hereinafter.
FIG. 1 is a view showing a display device according to the related art.
In FIG. 1, a display device 10 according to the related art includes a display panel 20, first to third printed circuit boards (PCBs) 40, 42 and 44, first and second flexible films 50 and 52, and a plurality of chip on films (COFs) 60.
A connector 40a, a timing controlling part 30 and a power part 32 are formed on the first PCB 40. The timing controlling part 30 and the power part 32 may be formed as an integrated circuit (IC).
When an external power, an image signal and a plurality of timing signals are inputted through the connector 40a from an external system, the power part 32 generates and outputs a power for the display device 10, and the timing controlling part 30 generates and outputs an image data and a plurality of control signals using the image signal and the plurality of timing signals.
In addition, first and second PCB lines 70 and 78 are formed on the first PCB 40. The first PCB line 70 transmits the power outputted from the power part 32, and the second PCB line 78 transmits the image data and the plurality of control signals outputted from the timing controlling part 30.
First film lines 72a and 72b and second film lines 80a and 80b are formed on each of the first and second flexible films 50 and 52. The first film lines 72a and 72b transmit the power of the first PCB 40 to the second and third PCBs 42 and 44, and the second film lines 80a and 80b transmit the image data and the plurality of control signals of the first PCB 40 to the second and third PCBs 42 and 44.
Third PCB lines 74a and 74b and fourth PCB lines 82a and 82b are formed on each of the second and third PCBs 42 and 44. The third PCB lines 74a and 74b transmit the power from the first and second flexible films 50 and 52 to the plurality of COFs 60, and the fourth PCB lines 82a and 82b transmit the image data and the plurality of control signals from the first and second flexible films 50 and 52 to the plurality of COFs 60.
A data driving part 34 is formed on each of the plurality of COFs 60. The data driving part 34 may be formed as an IC. The data driving part 34 generates and outputs a data signal using the image data and the plurality of control signals transmitted from the second and third PCBs 42 and 44.
In addition, first and second COF lines 76 and 84 are formed on each of the plurality of COFs 60. The first COF lines 76 transmit the power from the second and third PCBs 42 and 44 to the data driving part 34, and the second COF lines 84 transmit the image data and the plurality of control signals from the second and third PCBs 42 and 44 to the data driving part 34.
The display panel 20 displays the image using the data signal outputted from the data driving part 34.
The image data, the plurality of control signals and the power of the timing controlling part 30 and the power part 32 are transmitted to the data driving part 34, and the data signal of the data driving part 34 is transmitted to the display panel 20, thereby the image is displayed. In the display device 10 having a large size over 29 inch or 30 inch, a plurality of pads of the first PCB 40 having a large size corresponding to the display panel 20 having a large size are not directly aligned with a plurality of pads of the plurality of COFs 60 because of a difference in coefficients of thermal expansion between the first PCB 40 and the plurality of COFs 60.
In the display device 10 having a large size, as a result, the second and third PCBs 42 and 44 are connected to the plurality of COFs 60 that is connected to the display panel 20, and the first PCB 40 is connected to the second and third PCBs 42 and 44 using the first and second flexible films 50 and 52 so that the image data, the plurality of control signals and the power of the timing controlling part 30 and the power part 32 can be transmitted to the data driving part 34.
However, since the number of the PCBs increases and the number of the flexible films such as a flexible printed circuit (FPC) and a flexible flat cable (FFC) increases, structure and fabrication process become complicated and fabrication cost increases. In addition, fabrication time increases due to increase of a connection process, and deterioration in the connection process increases.